Hertz-SSE

(This is a community driven project)

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Server-Sent events is a specification for implementing server-side-push for web frontend applications, through plain-old HTTP. The Server-Sent Events EventSource API is standardized as part of HTML5[1] by the W3C. This repository is a fork of manucorporat/sse and r3labs/sse for Hertz.

Install

go get github.com/hertz-contrib/sse

Example

Server

package main

import (
  "context"
  "net/http"
  "time"

  "github.com/hertz-contrib/sse"

  "github.com/cloudwego/hertz/pkg/app"
  "github.com/cloudwego/hertz/pkg/app/server"
  "github.com/cloudwego/hertz/pkg/common/hlog"
)

func main() {
  h := server.Default()

  h.GET("/sse", func(ctx context.Context, c *app.RequestContext) {
    // client can tell server last event it received with Last-Event-ID header
    lastEventID := sse.GetLastEventID(c)
    hlog.CtxInfof(ctx, "last event ID: %s", lastEventID)

    // you must set status code and response headers before first render call
    c.SetStatusCode(http.StatusOK)
    s := sse.NewStream(c)
    for t := range time.NewTicker(1 * time.Second).C {
      event := &sse.Event{
        Event: "timestamp",
        Data:  []byte(t.Format(time.RFC3339)),
      }
      err := s.Publish(event)
      if err != nil {
        return
      }
    }
  })

  h.Spin()
}

Client

package main

import (
  "context"
  "sync"

  "github.com/hertz-contrib/sse"

  "github.com/cloudwego/hertz/pkg/common/hlog"
)

var wg sync.WaitGroup

func main() {
  wg.Add(2)
  go func() {
    // pass in the server-side URL to initialize the client	  
    c := sse.NewClient("http://127.0.0.1:8888/sse")

    // touch off when connected to the server
    c.SetOnConnectCallback(func(ctx context.Context, client *sse.Client) {
      hlog.Infof("client1 connect to server %s success with %s method", c.GetURL(), c.GetMethod())
    })

    // touch off when the connection is shutdown
    c.SetDisconnectCallback(func(ctx context.Context, client *sse.Client) {
      hlog.Infof("client1 disconnect to server %s success with %s method", c.GetURL(), c.GetMethod())
    })

    events := make(chan *sse.Event)
    errChan := make(chan error)
    go func() {
      cErr := c.Subscribe(func(msg *sse.Event) {
        if msg.Data != nil {
          events <- msg
          return
        }
      })
      errChan <- cErr
    }()
    for {
      select {
      case e := <-events:
        hlog.Info(e)
      case err := <-errChan:
        hlog.CtxErrorf(context.Background(), "err = %s", err.Error())
        wg.Done()
        return
      }
    }
  }()

  go func() {
    // pass in the server-side URL to initialize the client	  
    c := sse.NewClient("http://127.0.0.1:8888/sse")

    // touch off when connected to the server
    c.SetOnConnectCallback(func(ctx context.Context, client *sse.Client) {
      hlog.Infof("client2 %s connect to server success with %s method", c.GetURL(), c.GetMethod())
    })

    // touch off when the connection is shutdown
    c.SetDisconnectCallback(func(ctx context.Context, client *sse.Client) {
      hlog.Infof("client2 %s disconnect to server success with %s method", c.GetURL(), c.GetMethod())
    })

    events := make(chan *sse.Event)
    errChan := make(chan error)
    go func() {
      cErr := c.Subscribe( func(msg *sse.Event) {
        if msg.Data != nil {
          events <- msg
          return
        }
      })
      errChan <- cErr
    }()
    for {
      select {
      case e := <-events:
        hlog.Info(e)
      case err := <-errChan:
        hlog.CtxErrorf(context.Background(), "err = %s", err.Error())
        wg.Done()
        return
      }
    }
  }()

  wg.Wait()
}

Real-world examples

This repository comes with two server-examples to demonstrate how to build realtime applications with server-sent event.

Stock Price (examples/server/stockprice)

A web server that push (randomly generated) stock price periodically.

Run exmaples/server/chat/main.go to start server.
Send a GET request to /price

curl -N --location 'localhost:8888/price'
#id:1681141432283
#event:AAPL
#data:92.607347
#
#id:1681141432283
#event:AMZN
#data:73.540894
#
#id:1681141433283
#event:AAPL
#data:23.536702
#
#id:1681141433283
#event:AMZN
#data:63.156229
#

Chat Server (examples/server/chat)

A chat server that push new messages to clients using server-sent events. It supports both direct and broadcast messaging.

Run examples/server/chat/main.go to start server.
Send a get request to /chat/sse.

# receive message on behalf of user hertz
curl -N --location 'http://localhost:8888/chat/sse?username=hertz'

Open a new terminal and send messages to hertz.

# send a broadcast message
curl --location --request POST 'http://localhost:8888/chat/broadcast?from=kitex&message=cloudwego'
# send a direct message
curl --location --request POST 'http://localhost:8888/chat/direct?from=kitex&message=hello%20hertz&to=hertz'

On the first terminal, you should see 2 messages.

curl -N --location 'http://localhost:8888/chat/sse?username=hertz'
#event:broadcast
#data:{"Type":"broadcast","From":"kitex","To":"","Message":"cloudwego","Timestamp":"2023-04-10T23:48:55.019742+08:00"}
#
#event:direct
#data:{"Type":"direct","From":"kitex","To":"hertz","Message":"hello hertz","Timestamp":"2023-04-10T23:48:56.212855+08:00"}

Benchmark Results

All benchmarks are stored for each commit, they can be viewed here:

https://hertz-contrib.github.io/sse/benchmarks/